In a previous patent, U.S. Pat. No. 5,038,537, issued Aug. 13, 1991, I describe a window system and structure utilizing aluminum. The purpose of this prior patent was to teach my development of a practical system for the replacement of windows in Art Deco buildings 50 years old and older that are now designated as landmarks by federal, state, and municipal agencies. These original steel windows with their elegant, slim casements represented modernity and high technology to architects working in the Bauhaus, Art Deco, and Streamlined styles. The characteristics of these steel window structures were:
1. A two inch masonry-to-glass perimeter sight line. PA1 2. A three inch glass-to-glass sight line at operable to operable and operable to fixed framing members. PA1 3. A putty slope, mitered corner appearance around each operable and fixed light with exterior face of glass set back one inch from face of exterior window frame. PA1 4. An uninterrupted narrow reveal around casement leaves. PA1 5. Endless elevation layouts combining fixed and operable lights, where operable lights are virtually indistinguishable from fixed lights.
An object of U.S. Pat. No. 5,038,537 was to provide a practical and economical aluminum window structure to accommodate modern day, double paned insulating glass which is typically 1" thick, and to do so in a manner to duplicate the classic, narrow appearance of the original steel windows. While this object was substantially accomplished in this prior invention, the smallest glass-to-glass sight line that could be obtained was 3" due to the strength limitations of aluminum. To provide even narrower masonry-to-glass and glass-to-glass sight lines as low as, for example, 13/4" would be aesthetically more desirable from the point of view of replacement windows in "significant" older buildings, and also, in the opinion of many current day architects, for new buildings. The instant invention addresses this problem by returning to steel as the main structural material for the window frame.
The basic problem with the old style steel window is that they measure about 11/4" to 13/4" from front to back, which does not provide enough space to install modern day 1" thick insulating glass generally agreed to be the most efficient for strength and energy conservation. To overcome this it is current practice with steel window frames to use longer legged frame members for operating ventilators, such as, for example, casements and awnings. This results in windows which are 40 to 50% wider at the glass-to-glass sight lines because insulating glass requires greater edge engagement and edge tolerance than monolithic non-insulating glass.
Additional problems with current steel window frame construction is that today windows are almost universally glazed from the interior and not from exterior scaffolding. This has given rise to a "flat" exterior appearance of the windows in contrast to the prior protruding portion of the depth of the bars which lent interesting shadows and texture to the older buildings facade. Interior glazing also virtually mandates factory painting and not painting in the field. For economy and convenience both the exterior and interior portion of the steel frame receive the same finish. These finishes must be ultra-violet light resistance, and usually have a shiny finish. Of course, these requirements do not apply to the interior frame which is not exposed to the weather and so could be finished in an entirely different coating.
Another problem with current steel frame window construction is that both the internal and external sections are monolithic, hot rolled steel sections with no provision for any thermal break. While steel has only 1/3 the conductivity of aluminum there is still significant conduction from the exterior to the interior framing members. And the relatively rough surfaces of hot rolled steel present an opportunity for significant air leakage around these frames. Additionally the current steel frame structures rule out the use of "Tuck" or "Jiggle" glazing of the windows, which allows the frame to retain its strength for handling, and permits the interior glazing of fixed lights at the same time.
It is to the above and additional problems which will be discussed below that the instant invention is addressed.
It is therefore a primary object of the present invention to provide a steel window structure which aesthetically replicates the steel window of old while responding to current performance demands of government and industry.
It is an additional object of the present invention to provide a steel window structure with an inherent thermal break between the exterior and interior portions of the frame.
It is a further object of the invention to provide a steel window structure with different factory applied coatings to the exterior and interior portions of the frame.
Another object of the invention is to provide a steel window structure which permits internal "Tuck" or "Jiggle" glazing of the windows.
It is an additional object of the invention to provide for having fixed and operable lights within the same perimeter mainframe wherein they all appear with a uniform profile when viewed from the exterior.